1. Field of the Invention
The present invention relates to a control circuit and a control method for controlling the acceleration and deceleration of a stepping motor, and in particular, to stepping motor driving pulse generation technology used to control the acceleration and deceleration of a stepping motor. In further detail, the present invention relates to a stepping motor control circuit and a stepping motor control method for an image forming apparatus such as an electrostatic recording type or electrophotographic recording type copier or printer that uses a stepping motor.
2. Related Background Art
Conventionally, for example, in an electrophotographic image forming apparatus, a DC brushless motor is used for a driving source for the conveyance of paper such as recording sheet, a driving force is transmitted from this motor to each driving part through a gear, an electromagnetic clutch, etc., and sequence operation is achieved by ON/OFF of the electromagnetic clutch.
In addition, in a high speed machine having plenty of outputs of printouts per unit time in recent years, it has also become common to have the construction of accurately controlling the conveying operation of recording sheet by using a stepping motor and by increasing the stability of high-speed paper conveyance instead of the ON/OFF of drive by an electromagnetic clutch. In order to achieve such high-speed paper conveyance, it is necessary to accelerate a stepping motor up to a predetermined velocity in a short time, and hence, for example, a stepping motor control circuit controlled by an eight-step step period setting value as shown in FIGS. 4A and 4B has been used for the acceleration and deceleration of the stepping motor.
In FIG. 4A, a register 206 controls the start and stop, and acceleration and deceleration of a motor by setting a start control signal (ON signal) controlling the start of the motor, a setting value of step change time for acceleration for setting step change timing under acceleration, a setting value of step change time for deceleration for setting step change timing under deceleration, and a change-over signal for acceleration and deceleration (ACC/DEC signal), through a CPU bus from a CPU not shown in the figure.
In FIG. 4A, a step change timer 201 for acceleration and deceleration outputs a step change timing pulse according to the value set by the setting value of step change time for acceleration during acceleration, and outputs s step change timing pulse according to the value established by the setting value of step change time for deceleration during deceleration.
Every time the above-mentioned step change timing pulse is inputted, a step control circuit 202 increases a step value during acceleration and decreases a step value during deceleration. For example, when the step change timing pulse is inputted in every 16 ms according to the setting of the setting value of step change time for acceleration, the step value is incremented as 0xe2x86x921xe2x86x922xe2x86x923 in every 16 ms.
A selector 203 selects one value among from a step-0 setting value to a step-7 setting value according to the above-mentioned step value inputted from the step control circuit 202, and outputs the value as a driving pulse period. In the case that values of respective steps are set beforehand as shown in the table in FIG. 4B, for example, when an inputted step value is 3, the setting value is 195, and hence, the selector 203 outputs this data, 195 as the driving pulse period.
A driving pulse generation circuit 204 generates a drive pulse to drive a stepping motor 205 according to the driving pulse period (setting value) inputted from the selector 203. In the case that values of respective steps are set as shown in the table in FIG. 4B, since the inputted setting value is 1040 at step 0, the driving pulse generation circuit 204 outputs the driving pulse after taking a count of 1040 based on a 10 xcexcs timer, and hence, the driving pulse period becomes 10.4 ms, and its frequency becomes 96.2 PPS. Similarly, since the driving pulse generation circuit 204 outputs the driving pulse after taking a count of 547 based on the 10-xcexcs timer at step 1, the driving pulse period becomes 5.47 ms, and its frequency becomes 182.8 PPS. Similarly, since the driving pulse generation circuit 204 outputs the driving pulse after taking a count of 299 based on the 10 xcexcs timer at step 2, the driving pulse period becomes 2.99 ms, and its frequency becomes 334.4 PPS.
In this manner, when the driving pulse is generated by the driving pulse generation circuit 204, the change of the driving pulse frequency becomes as shown in a graph in FIG. 5, which becomes large-step-formed velocity control. In the figure, a bar chart shows the frequency, and a line graph shows the period.
Nevertheless, when it was made to accelerate or decelerate a motor (stepping motor) in a small number of steps as mentioned above, the frequency change between the velocity steps was large. Therefore, there was a problem that the motor stepped out even if it was made to enlarge a torque margin of the motor. In addition, since registers corresponding to the number of setting values became necessary when it was made to increase the number of steps of the step period setting value, there was a problem that the circuit scale of the stepping motor control circuit became large because the registers increased.
The present invention aims to provide a stepping motor control circuit and a stepping motor control method that can make it possible to accelerate and decelerate a motor without stepping out even if there is no excessive torque margin by performing the control of artificially increasing the number of steps without enlarging the circuit scale of the stepping motor control circuit.
An aspect of the present invention is characterized in a stepping motor control circuit that generates a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a plurality of setting values of each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating the above-described stepping motor, and period calculating means of finding a driving pulse period by calculating so as to divide each difference between driving pulse periods in between respective setting values into s predetermined number of pieces.
In addition, this is characterized in controlling the above-described stepping motor based on the driving pulse period found by the above-described period calculating means.
Moreover, this is characterized in the plurality of above-described setting values, each comprising a start setting value corresponding to a number of start velocity steps at the time of starting the above-described stepping motor, and a difference setting value that becomes a difference between respective velocity steps.
Another aspect of the present invention is characterized in a stepping motor control circuit that generates a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a register setting a plurality of setting values of each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating the above-described stepping motor, and period calculating means of finding a driving pulse period by calculating so as to divide each difference between driving pulse periods in between respective setting values, set by the above-described register, into a predetermined number of pieces.
In addition, this is characterized in controlling the above-described stepping motor based on the driving pulse period found by the above-described period calculating means.
Moreover, this is characterized in the plurality of above-described setting values, each comprising a start setting value corresponding to a number of start velocity steps at the time of starting the above-described stepping motor, and a difference setting value that becomes a difference between respective velocity steps.
In addition, still another aspect of the present invention is characterized in a stepping motor control circuit that generates a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising step control means of outputting a main step value and a sub step value according to a timing pulse, and period calculating means of finding a driving pulse period based on a plurality of setting values each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating the above-described stepping motor, the above-described main step value, and the above-described sub step value.
Moreover, this is characterized in the plurality of above-described setting values, each comprising a start setting value corresponding to a number of start velocity steps at the time of starting the above-described stepping motor, and a difference setting value that becomes a difference between respective velocity steps.
In addition, the above-described period calculating means is characterized in finding a driving pulse period based on the above-described start setting value and the above-described difference setting value according to the above-described main step value and the above-described sub step value.
Furthermore, still another aspect of the present invention is characterized in a stepping motor control circuit that generates a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a step timer generating a timing pulse for step change, step control means of outputting a main step value and a sub step value according to the above-described timing pulse for step change, period calculating means of finding a driving pulse period according to the above-described main step value and sub step value based on a plurality of setting values each comprising of a start setting value, corresponding to a number of velocity steps at the time of starting the above-described stepping motor, and a difference setting value corresponding to a difference between respective velocity steps.
Moreover, the above-described step timer is characterized in generating a timing pulse for step change based on a start control signal, a setting value of step change time, and a change-over signal for acceleration and deceleration.
A still another aspect of the present invention is characterized in a stepping motor control method for generating a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a step of changing each driving pulse period so as to divide each difference between driving pulse periods in between respective setting values into a predetermined number of pieces for a plurality of setting values of each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating the above-described stepping motor.
In addition, this is characterized in a step of controlling the above-described stepping motor based on the driving pulse period found.
Moreover, this is characterized in the plurality of above-described setting values, each comprising a start setting value corresponding to a number of start velocity steps at the time of starting the above-described stepping motor, and a difference setting value that becomes a difference between respective velocity steps.
Furthermore, still another aspect of the present invention is characterized in a stepping motor control method for generating a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a step of generating a main step value and a sub step value according to a timing pulse, and a step of finding a driving pulse period based on a plurality of setting values each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating the above-described stepping motor, the above-described main step value, and the above-described sub step value.
Moreover, this is characterized in the plurality of above-described setting values, each comprising a start setting value corresponding to a number of velocity steps at the time of starting the above-described stepping motor, and a difference setting value that becomes a difference between respective velocity steps.
In addition, the above-described period calculating means is characterized in finding a driving pulse period based on the above-described start setting value and the above-described difference setting value according to the above-described main step value and the above-described sub step value.
Furthermore, still another aspect of the present invention is characterized in a stepping motor control method for generating a driving pulse controlling the acceleration and deceleration of a stepping motor, comprising a step of generating a timing pulse for step change, a step of generating a main step value and a sub step value according to the above-described timing pulse for step change, and a step of finding a driving pulse period according to the above-described main step value and sub step value based on a plurality of setting values each comprising a start setting value, corresponding to a number of velocity steps at the time of starting the above-described stepping motor, and a difference setting value corresponding to a difference between respective velocity steps.
In addition, the above-described step of generating a timing pulse for step change is characterized in generating a timing pulse for step change based on a start control signal, a setting value of step change time, and a change-over signal for acceleration and deceleration.
Other objects and features of the present invention will become obvious from the following description and drawings.